The invention relates to a fifth wheel coupling for a releasable connection between a semi-trailer and a truck tractor with a fifth wheel plate and a pair of pillow blocks for attaching the fifth wheel coupling to the frame of the truck tractor, wherein
the fifth wheel plate is connected to the pillow blocks in such a way that it pivots around an axis running parallel to the foot print of the truck tractor and perpendicular to the longitudinal axis of the truck tractor;
the underside of the fifth wheel plate is equipped with a pair of hollow cylindrical bearing troughs arranged coaxially to the axis, while the pillow blocks have corresponding cylindrical bearing surfaces;
the pillow blocks are equipped with an eye located below the bearing surfaces to allow for fasteners to penetrate the same in the form of a bridge connecting the fifth wheel plate to the pillow blocks in such a way that it swivels around the axis; and
a bearing shell is disposed between the bearing trough and the bearing surface, while a damping element is disposed between the bridge and the upper interior wall of the eye.
The means formerly used to mount fifth wheel couplings of this kind on the frame of a truck tractor were separate mounting plates which could be adjusted to different lateral distances between the longitudinal members of the frame of the truck tractor and whereon the pillow blocks of the fifth wheel coupling were attached at a firmly specified lateral distance from one another. For some time now, these mounting plates have no longer been used, in order to reduce weight and height. This led to the necessity for designing fifth wheel couplings for differing frame widths. It is true that these only vary within a narrow range because on the one hand, the outer dimensions of the semi-trailers and the truck tractors are limited by law and on the other hand, the tire width is standardized which inevitably leads to an upper limit for the frame width.
The body manufacturers have adapted to this circumstance, and for economic reasons produce the cross braces located between the longitudinal members of the frame in only one length for practical reasons. This results in frames of uniform width if profiles, usually I-profiles, with webs of equal thickness were always used. For price and weight-related reasons, however, light and heavy truck tractors use profiles having the same shape, but differing flange and web thicknesses, and different mounting widths become necessary for the attachment of the fifth wheel couplings, as well.
These components are more complicated and subject to higher stress, therefore they require complex and costly manufacturing processes and can only be produced economically in large quantities with the same dimensions. The object of the invention is therefore to demonstrate possibilities of adjusting uniformly manufactured fifth wheel couplings to frames with differing widths. In this context, various possibilities from the patent application DE 199 52 997 A1 have become known to the art.
In a first solution, two pairs of bores for the attachment of the bridges are provided in the fifth wheel plate, whereby a width adjustment stepped by the axial hole distance becomes possible. A fine adjustment is facilitated when the mounting flanges of the pillow blocks resting on top of the frame are equipped with elongated holes oriented perpendicular to the longitudinal members.
A second solution stipulates a limitation of the bearing troughs by axially spaced contact surfaces. In this case, the axial distance is greater than the width of the pillow block. In order to achieve the step-by-step adjustment to differing frame widths, spacers are provided and inserted between the contact surfaces and the pillow block, said spacers possibly also being constructed as one-piece protrusions formed onto the bridge. This solution, as well, can be combined with elongated holes in horizontal mounting flanges.
In the solution described first, a relatively coarse step-by-step adjustment of the mounting width has to be provided because the distance between the bores cannot be chosen freely, but has a lower limit if the fifth wheel plate is not to become too weak in the area of the bores. This requires correspondingly long elongated holes and correspondingly wide horizontal mounting flanges for the pillow blocks.
In the solution described second, a disadvantage is perceived in the fact that the assembly is complicated by the additional spacers and that assembly errors may occur if xe2x80x9cinteriorxe2x80x9d and xe2x80x9cexteriorxe2x80x9d are confused during the insertion of the spacers or if they are not oriented in the same direction. This is also true for the installation of the bridges having protrusions formed onto them on one side.
Another disadvantage of the known fifth wheel coupling lies in the fact that the attachment is achieved with horizontal mounting flanges. In order to be able to vary the configuration of the fifth wheel coupling in the longitudinal direction of the frame, as well, the frame is conventionally equipped with rows of bores which are longer than the rows of bores in the mounting flange of the pillow blocks so that it becomes possible to adjust the point of attachment to various conditions, step by step. However, the upper and lower flanges of the I-shaped longitudinal members have to withstand far more stress than the web in the vicinity of the neutral zone and each bore in the upper flange thus means a weakening of the profile. Said weakness can be simply compensated by using a stronger profile, though this is associated with the disadvantage of an overdimensional profile in the area without holes.
Based on the aforesaid, there is not only the problem of width adjustment, but also the aspect that the advantage of reducing weight by omitting a separate mounting plate is not compensated by overdimensional longitudinal members or may even lead to a weight increase.
The invention therefore has the object of avoiding or at least diminishing a weakening of the longitudinal members when mounting the fifth wheel coupling on the frame of the truck tractor, and at the same time of providing closely stepped or even better, continuous width adjustment for the pillow block positions on the frame of the truck tractor.
This object is achieved according to the invention by the fact that the pillow blocks comprise a one-piece casting and are equipped with a vertical mounting flange for the direct lateral attachment to the longitudinal members of the frame of the truck tractor;
the bridges are equipped with cylindrical fitting surfaces matched to the hollow cylindrical bearing troughs, andxe2x80x94viewed on a longitudinal sectionxe2x80x94are constructed to be U-shaped and open on top, and have internal contact surfaces oriented perpendicular to the axis with an axial distance greater than the width of the pillow block in the area encircled by the bridge;
the bearing shellsxe2x80x94viewed on a longitudinal sectionxe2x80x94are constructed to be U-shaped and open at the bottom and have side walls with internal and external contact surfaces essentially vertical to the axis, wherein the distance of the external contact surfaces is adapted to the distance between the contact surfaces of the bridge, while the distance of the internal contact surfaces is adapted to the width of the pillow block in the encircled area;
xe2x80x83and that
viewed in the direction of the axis, the side walls are constructed with differing thicknesses to facilitate continuous adjustment to a given assembly width.
The direct attachment of the vertical mounting flanges of the pillow blocks to the web of the I-profiles of the longitudinal members makes it possible to omit the bores in the upper flange of the profiles and ensures that the profile is not weakened in this high-stress area. Therefore, it will not be necessary to provide longitudinal members that can withstand stress in the area with holes, and would necessarily be overdimensioned and thus unnecessarily heavy.
The use of vertical mounting flanges, however, excludes the provision of elongated holes for a step-by-step adjustment to differing frame widths. The known step-by-step adjustments, as for example by means of pairs of bores in the fifth wheel plate, can continue to be used. The required closely stepped or continuous adjustment is achieved according to the invention by the fact that the bridges are constructed as U-shaped with axially spaced contact surfaces and thatxe2x80x94viewed on a longitudinal sectionxe2x80x94U-shaped bearing shells are used wherein the axially limiting side walls can be constructed with differing thicknesses. If required, the appropriate coarsely stepped adjustment is provided for a given mounting width and then the thickness of the side walls of the bearing shells is determined in a way to obtain the still missing closely stepped adjustment.
In this context, it may be assumed that bearing shells will be used wherein the axial distance of the external contact surfaces of the side walls is adapted to the axial distance of the internal contact surfaces of the bridge and that the axial distance of the internal contact surfaces of the side walls is smaller than the width of the pillow block in the area encircled by the bridge. By machining with cutting tools, the axial distance of the internal contact surfaces is then enlarged as necessary by removing material either only on the external side wall, only on the internal side wall, or on both side walls, depending on the specified position of the pillow blocks. This is not particularly complicated or costly, because each bearing shell needs to be clamped only once on the lathe which can remove the material quickly and precisely, particularly from bearing shells manufactured of synthetic materials. Furthermore, this type of work is only necessary in isolated cases for the adjustment to a very unusual frame width. In most cases, the width will be more or less xe2x80x9cstandardizedxe2x80x9d where only manufacturing tolerances will have to be evened out. It is then possible to assume the use of pre-fabricated bearing shells with side walls of fixed thickness and make use of the possibility of an installation with a rotation by 180xc2x0 which permits implementation of three different mounting widths in each case.
It is therefore possible to cover the entire range between two coarsely adjustable mounting widths with only few types of thickness differences in the side walls by such closely stepped adjustment that the above described individual adjustment by means of removing material is not necessary.